JP2003092196A - High voltage discharge lamp switching device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small and inexpensive high voltage discharge lamp switching device without a conventional condenser as a power source for generation of high voltage pulses in a generation circuit of high voltage pulses generating the high voltage pulses for starting the high pressure discharge lamp and without any switching element having a large current capacity. SOLUTION: In the high voltage discharge lamp switching device for generating high voltage pulses in the high voltage side of a transformer, which generates the high voltage for starting the high voltage discharge lamp and connected in series with the high voltage discharge lamp, and current is passed via the switching element through the low voltage coil of the transformer, a resistance is connected to the low voltage side of the switching element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high pressure discharge lamp lighting device, and more particularly to a high voltage pulse generating circuit for starting a high pressure discharge lamp.

[0002]

2. Description of the Related Art FIG. 3 shows, for example, Japanese Patent Laid-Open No. 2000-3066.
It is a block diagram which shows the structure of the conventional high pressure discharge lamp lighting device disclosed by the 88 publication. In FIG. 3, 1 is an AC power supply, 2 is a diode bridge for full-wave rectifying an AC voltage,
3 is an active filter for converting the output voltage of the diode bridge 2 into a DC voltage with high power factor, 4 is a current limiting circuit for controlling the current flowing through the high pressure discharge lamp 7 so that the electric power of the high pressure discharge lamp 7 is constant, Reference numeral 5 is an inverter for converting the DC voltage output from the current limiting circuit 4 into a low-frequency AC voltage. 6
Is a high-voltage pulse generating circuit for generating a high-voltage pulse for starting the high-pressure discharge lamp 7.
e, a self-extinguishing type MOS-FET (switching element) 6d that can be turned on / off by an external control signal, and the output voltage of the active filter 3 is a diode 6a and a resistor 6b.
The high voltage pulse generated in the capacitor 6c and the pulse transformer 6e charged via the
It is composed of a capacitor 6f that blocks so as not to go around.

Reference numeral 13 calculates a target current to be supplied to the high-pressure discharge lamp 7 on the basis of the discharge lamp voltage detected by the discharge lamp voltage detection circuit 12, and the active filter 3,
Current limiting circuit 4, inverter 5, and high voltage pulse generation circuit 6
Is a control circuit for controlling each. Reference numeral 8 is a control power supply circuit that generates power for the control circuit 13, 9 is an active filter output voltage detection circuit, and 10 is a discharge lamp current detection resistor 1.
It is a differential amplifier that controls so that the discharge lamp current detected in 1 and the target current output from the control circuit 13 match.

Next, the operation will be described with reference to FIG. When the AC power supply 1 is turned on, the control power supply circuit 8 first generates a control power supply and applies it to the control circuit 13. The control circuit 13 starts the operation of the active filter 3 and controls so that the output voltage of the active filter 3 becomes a predetermined DC voltage. Further, the control circuit 13 outputs a target current to the differential amplifier 10. The differential amplifier 10 compares the target current output from the control circuit 13 with the actually flowing discharge lamp current detected by the discharge lamp current detection resistor 11 so that the target current and the actually flowing discharge lamp current match. To control the current limiting circuit 4.

Since the high-pressure discharge lamp 7 is not turned on when the power is turned on, the output voltage of the active filter 3 is directly output to the output of the current limiting circuit 4. This DC voltage is converted into an AC voltage by the inverter 5 and applied to the high-pressure discharge lamp 7, and the capacitor 6c is charged via the diode 6a and the resistor 6d of the high-voltage pulse generation circuit 6. When the charging of the capacitor 6c is completed, the control circuit 13 drives the switching element 6d.

When the switching element 6d is turned on, the electric charge charged in the capacitor 6c flows into the switching element 6d via the pulse transformer 6e. Since the winding n2 on the high-pressure discharge lamp 7 side of the pulse transformer 6e is configured with about 10 times the number of turns of the winding n1 on the switching element 6d side, a high voltage about 10 times the voltage of n1 is applied to the pulse transformer 6e. The high-voltage pulse generated on the winding n2 side of 6e is superimposed on the AC voltage output from the inverter 5 and applied to the high-pressure discharge lamp 7 to cause dielectric breakdown of the high-pressure discharge lamp 7.

In FIG. 4, the high-voltage pulse generating circuit 6 generates a high-voltage pulse and applies it to the high-pressure discharge lamp 7,
Shows the operation waveforms of each part until the occurrence of dielectric breakdown. There are two possible processes for causing the dielectric breakdown. In the figure, Case 1 is the waveform shown by (a1) to (a4), and Case 2 is the waveform shown by (b1) to (b4).

The above two cases of dielectric breakdown are in the state of the high-pressure discharge lamp 7, that is, when the temperature of the lamp itself is relatively high, such as when a sufficient time has not passed since the lamp was turned off, and dielectric breakdown is unlikely to occur. In case 1, as in case 1, dielectric breakdown occurs with a high voltage pulse, and when the temperature of the lamp itself is low and dielectric breakdown is likely to occur, as in case 2, dielectric breakdown occurs with a relatively low high voltage pulse.

The high voltage pulse generation circuit 6 for generating a high voltage pulse is composed of the pulse transformer 6e, the switching element 6d, the capacitor 6c and the capacitor 6f charged through the diode 6a and the resistor 6b as described above. However, in the process of dielectric breakdown, the resistor 6b
The necessity of the capacitor 6c and the necessity of the capacitor 6c will be described below with reference to FIG.

In the figure, (a1) and (b1) are drive signals for the switching element 6d, (a2) and (b2) are terminal voltages of the capacitor 6c, (a3) and (b3) are currents flowing through the switching element 6d, (A4) and (b4) represent high voltage pulses generated on the winding side (n2 winding) of the pulse transformer 6e connected in series to the high pressure discharge lamp 7.

First, operation waveforms (a1) to (a4) of case 1 will be described. When the switching element 6d is driven by the drive signal shown in (a1), the pulse transformer 6e
The current increases with a gradient determined by the inductance value of the winding (n1 winding) on the side connected in series to the switching element 6d. Since the current is supplied from the capacitor 6c, the capacitor 6c discharges and the terminal voltage decreases as shown in (a2). Since the current also decreases as the terminal voltage drops, the current flowing through the switching element 6d becomes (a
Draw an arc as in 3). This current is the pulse transformer 6e
The voltage also flows to the n1 winding of the pulse transformer 6e to generate a voltage. Since the n2 winding of the pulse transformer 6e has about 10 times the number of turns of the n1 winding, a high voltage pulse about 10 times of the n1 winding appears in the n2 winding.

After the switching element 6d is turned off, the energy accumulated in the winding n1 of the pulse transformer 6e is released to the winding n2 side, and a high voltage pulse appears in the n2 winding. In case 1, this switching element 6d
As shown in (a4) which occurs after turning off the high voltage discharge lamp 7, the high voltage discharge lamp 7 is dielectrically broken down by the reverse high voltage pulse.

Next, operation waveforms (b1) to (b4) of case 2 will be described. When the switching element 6d is driven by the drive signal shown in (b1), as shown in (b4), the high-pressure discharge lamp 7 causes dielectric breakdown with a relatively low pulse immediately after the driving of the switching element 6d is started. In this case, the dielectric breakdown causes the n2 winding to be in a short-circuit state, the mutual inductance value to be small, and the inductance of the n1 winding to be small. As a result, (b3)
As shown in, a larger current flows through the switching element 6d than in case 1 above.

Therefore, the current capacity of the switching element 6d must have a margin with respect to the excessive current of the case 2. Further, in the case where the capacitor 6c and the resistor 6b are removed and the power source of the high-voltage pulse generation circuit 6 is directly taken from the active filter 3, and the case 2 occurs, the current is continuously supplied from the active filter 3. Since an excessive current flows into the switching element 6d, the capacitor 6c and the resistor 6b are required.

[0015]

In view of the above, the conventional high pressure discharge lamp device has a high voltage pulse generating circuit 6 for generating a high voltage pulse for starting the high pressure discharge lamp 7,
Since the high withstand voltage capacitor 6c and the switching element 6d having a large current capacity are required, there is a problem that the lighting device becomes large and the cost becomes high.

The present invention has been made in order to solve the above problems, and it is a switching element 6d having a large current capacity.
It is an object of the present invention to obtain an inexpensive and compact high-pressure discharge lamp device by using a high-voltage pulse generation circuit configuration that does not use the capacitor 6c and does not require the capacitor 6c.

[0017]

Claim 1 according to the present invention
In the high-pressure discharge lamp lighting device described above, a transformer for generating a high voltage for starting the high-pressure discharge lamp is connected in series to the high-pressure discharge lamp, and a current is supplied to a low-voltage side winding of the transformer via a switching element. In a high-pressure discharge lamp lighting device that generates a high-voltage pulse on the high-voltage side winding of the transformer, a resistor is connected to the low-voltage side of the switching element.

Further, in the high pressure discharge lamp lighting device according to the present invention, the resistance connected to the switching element is 0.5Ω.
That is all.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. 1 is a block diagram showing a configuration of a high pressure discharge lamp lighting device according to Embodiment 1 of the present invention. In FIG. 1, the same or corresponding parts as those of the conventional example are designated by the same reference numerals and the description thereof will be omitted. Reference numeral 6'denotes a high voltage pulse generation circuit for generating a high voltage pulse for starting the high pressure discharge lamp 7, and a pulse transformer 6e,
For example, having a gate terminal, a drain terminal, a source terminal,
Self-extinguishing MO that can be turned on / off by an external control signal
It is composed of a switching element 6d of the S-FET, a capacitor 6f that blocks a high voltage pulse generated in the pulse transformer 6e from sneaking into the inverter 5, and a resistor 6g connected to the low voltage side of the switching element 6d.

Next, the operation will be described with reference to FIG. When the AC power supply 1 is turned on, the control power supply circuit 8 first generates a control power supply and applies it to the control circuit 13. The control circuit 13 starts the operation of the active filter 3 and controls so that the output voltage of the active filter 3 becomes a predetermined DC voltage. Further, the control circuit 13 outputs the target current to the differential amplifier 10. The differential amplifier 10 includes the control circuit 1
3 is compared with the actual discharge lamp current detected by the discharge lamp current detection resistor 11 and the current limiting circuit 4 is connected so that the target current and the actual discharge lamp current match. Control.

Since the high-pressure discharge lamp 7 is not turned on when the power is turned on, the output voltage of the active filter 3 is directly output to the output of the current limiting circuit 4. The output DC voltage is converted into an AC voltage by the inverter 5 and applied to the high pressure discharge lamp 7. Further, the control circuit 13 outputs a drive signal to the switching element 6d to drive the switching element 6d.

When the switching element 6d is turned on, a current flows from the active filter 3 to the switching element 6d via the pulse transformer 6e. At this time, the winding n2 on the high-pressure discharge lamp 7 side of the pulse transformer 6e is configured with about 10 times the number of turns of the winding n1 on the switching element 6d side, so that the winding n2 has a high voltage about 10 times the voltage of the winding n1. A voltage pulse is generated on the n2 side winding of the pulse transformer 6e,
The high voltage pulse is superimposed on the AC voltage output from the inverter 5 and applied to the high pressure discharge lamp 7 to cause dielectric breakdown of the high pressure discharge lamp 7.

FIG. 2 shows operation waveforms of each part until the high voltage pulse generation circuit 6'generates a high voltage pulse and applies it to the high pressure discharge lamp 7 until the high voltage discharge lamp 7 causes dielectric breakdown. is there. In FIG. 2, (A) shows the switching element 6
d is a drive signal, (B) is a current flowing through the switching element 6d, and (C) is a high voltage pulse generated on the winding side (n2 winding) of the pulse transformer 6e connected in series to the high pressure discharge lamp 7. ing.

Next, the operation waveforms of FIG. 2 will be described with reference to FIG. As shown in FIG. 2C, the high-pressure discharge lamp 7 is dielectrically broken down by the relatively low high-voltage pulse generated in the n2 winding of the pulse transformer 6e immediately after the switching element 6d is driven, and the inductance of the n1-side winding is increased. When the value becomes smaller and the current flowing through the switching element 6d increases as shown in (B), the same current also flows through the resistor 6g connected to the switching element 6d, causing a voltage drop in the resistor 6g. . Therefore, the switching element 6d
The source terminal voltage of is increased by a voltage drop with respect to the ground potential (zero potential). As a result, as shown in (A), the drive signal of the gate-source voltage of the switching element 6d is lowered by the voltage drop. Then, as the flowing current increases, the gate-source voltage decreases. The switching element 6d operates so as to limit the drain-source current when the gate-source voltage decreases.

For example, when a drive signal for the switching element 6d of 15V is applied to the gate terminal from the control circuit 13 and the resistance 6g is 0.5Ω and a current of, for example, 30A flows through the switching element 6d, Resistance 6
The voltage drop at g is 30 × 0.5 = 15V, and the source terminal is increased by 15V with respect to the ground potential. As a result, the gate voltage seen from the source terminal becomes zero V, so that the switching element 6d is turned off. That is, 30A
Even if the above current flows, the switching element 6d
Is turned off, so a current of 30 A or more does not flow.

As described above, since the resistor is connected to the low voltage side of the switching element of the high voltage pulse generating circuit for generating the high voltage pulse for starting the high pressure discharge lamp, an excessive current is applied to the switching element. When it flows, the switching element automatically turns off due to the voltage drop of the resistor, so a high-voltage pulse generation circuit can be configured without using a switching element with a large current capacity, and the conventional high-voltage pulse generation circuit In order to prevent an excessive current from flowing in the switching element, the charge was once stored in the capacitor and the high voltage pulse was generated by using this capacitor as the power supply. Since it is configured, an inexpensive and compact high pressure discharge lamp lighting device can be obtained.

In the above embodiment, the MOS-FET is used as the switching element, but the switching element is not limited to this, and an IGBT element, a bipolar transistor or the like may be used.

[0028]

As described above, in the high pressure discharge lamp lighting device according to the first aspect of the present invention, the current is caused to flow through the low voltage side winding of the transformer for generating the high voltage for starting the high pressure discharge lamp through the switching element. In a high pressure discharge lamp lighting device that generates a high voltage pulse on the high voltage side winding of a transformer, since a resistor is connected to the low voltage side of the switching element, if an excessive current flows in the switching element, Since the switching element automatically turns off due to the voltage drop, a high-voltage pulse generation circuit can be configured without using a switching element with a large current capacity. In order to prevent the current from flowing, the charge was once stored in the capacitor and this capacitor was used as a power source to generate high-voltage pulses.
Since the high-voltage pulse generating circuit does not require such a capacitor, an inexpensive and compact high-pressure discharge lamp lighting device can be obtained.

The high pressure discharge lamp lighting device according to claim 2 is
The resistance connected to the low voltage side of the switching element is set to 0.
Since it is set to 5Ω or more, for example, when the drive signal to the switching element is set to 15V, the current flowing in the switching element can be suppressed to 30A or less, and it is not necessary to use a switching element having a large current capacity.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a high pressure discharge lamp lighting device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing operation waveforms according to the first embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a conventional high pressure discharge lamp lighting device.

FIG. 4 is a diagram showing operation waveforms of a conventional high pressure discharge lamp lighting device.

[Explanation of symbols]

1 AC power supply, 2 diode bridge, 3 active filter, 4 current limiting circuit, 5 inverter,
6'High voltage pulse generation circuit, 7 High pressure discharge lamp, 8
Control power supply circuit, 9 active filter output voltage detection circuit, 10 differential amplifier, 11 discharge lamp current detection resistor, 12 discharge lamp voltage detection circuit, 13 control circuit.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masaomi Asayama             2-8-29 Kitayuki, Nishi-ku, Yokohama-shi, Kanagawa             Osram Melco Ltd. F term (reference) 3K072 AA11 AC11 DA08 DD07 GA03                       GB01                 3K083 AA85 AA91 BA05 BA25 BA41                       BC13 BC33 BC47 EA09

Claims (2)

[Claims] 1. A transformer for generating a high voltage for starting the high pressure discharge lamp is connected in series to the high pressure discharge lamp,
In a high-pressure discharge lamp lighting device that causes a current to flow in the low-voltage side winding of the transformer through a switching element to generate a high-voltage pulse in the high-voltage side winding of the transformer, a resistor is connected to the low-voltage side of the switching element. High-pressure discharge lamp lighting device characterized by. 2. The high pressure discharge lamp lighting device according to claim 1, wherein the resistance connected to the switching element is 0.5Ω or more.